ABSTRACT Influenza poses a significant health risk to the American public. Yearly flu vaccines are available for this illness, but they are not always effective. Sleep difficulties suppress immune functioning and may reduce the effectiveness of these vaccines. Many individuals work on shifts, and as such sleep difficulties (e.g. insomnia, shift-work disorder) are more likely in these populations. One such group is nurses. Nurses working in hospitals are in constant contact with medically fragile patients, and thus it is critical that they be well-protected. The primary goal of the proposed study is to develop a comprehensive model detailing the effects of sleep, assessed prospectively via actiwatches and sleep diaries one week before and one week after influenza vaccine, on influenza antibody response at 1-month follow-up and degradation of the response at 6-month and 12-month follow-up. Antibody amounts will be measured utilizing the hemagglutination inhibition (HI) assay. Four hundred nurses at a regional hospital (Denton Regional Medical Center ? DRMC) will be recruited to participate. The current design will allow assessment of antibody response to the influenza vaccine, as well as each individual viral strain. All immune assays will be performed at the Iowa State University Health and Human Performance research laboratory. Additional analyses will examine a meditational role between measures of sleep disturbance and a host of other variables (EMA data and pre-vaccine inflammatory cytokine levels) as predictors of antibody response.